Prairie Island Nuclear Generating Plant


CTLGroup was subcontracted by nuclear power generating station operators to assist in assessments of the concrete containment structures.  As a portion of those assessments the concrete has been examined by physical testing, chemical analyses and petrographic (microscopic) examinations.  In some of these instances, these laboratory evaluations were performed due to the leakage of borated water from the reactor components.

In instances where borated water had ponded on the containment concrete; cores and/or fractured concrete pieces were provided to the CTLGroup laboratory for analysis.  As these concrete cores and pieces were considered radioactively contaminated; CTLGroup’s radiation safety officer, Dr. Eli Port of Radiation Safety Services, Inc. (RSSI), evaluated all of the concrete before CTLGroup testing preceded.  Testing consisted of compressive strength testing, chemical analysis of powder samples, and petrographic evaluations.  As these tests are destructive in nature, continuous monitoring was required by RSSI during the testing procedures for fugitive particle contamination of the laboratory or of CTLGroup personnel.  Thus, CTLGroup developed protocols and procedures for the safe handling, sample preparation and testing of all of the specimens.

Petrographic analysis required that samples be cross sectioned, lapped and polished as well as sections prepared that were optically transparent (thin sectioned samples).  Due the radioactive nature of the specimens, cutting and polishing debris was controlled and collected during sample preparation.

The results of these laboratory investigations indicated that concrete subjected to ponded borated water was structurally sound.  Compression testing indicated strengths that were approximately 3,000 to 4,000 psi greater than expected.

Evaluations of the concrete microstructure, by petrography, indicated no degradation to the concrete microstructure and no expansive mineralization occurring within the concrete (a concern due to the ponded borated water).


Year of Operation


Megawatts of Power Produced
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